Sub-technique of T1556 Modify Authentication Process.View on attack.mitre.org
Adversaries may register malicious password filter dynamic link libraries (DLLs) into the authentication process to acquire user credentials as they are validated.
Windows password filters are password policy enforcement mechanisms for both domain and local accounts. Filters are implemented as DLLs containing a method to validate potential passwords against password policies. Filter DLLs can be positioned on local computers for local accounts and/or domain controllers for domain accounts. Before registering new passwords in the Security Accounts Manager (SAM), the Local Security Authority (LSA) requests validation from each registered filter. Any potential changes cannot take effect until every registered filter acknowledges validation.
Adversaries can register malicious password filters to harvest credentials from local computers and/or entire domains. To perform proper validation, filters must receive plain-text credentials from the LSA. A malicious password filter would receive these plain-text credentials every time a password request is made.
Rules on DetectionCode tagged with T1556.002.
| Rule | Level | Log source |
|---|---|---|
| Powershell Install a DLL in System Directory | high | windows / ps_script |
| Dropping Of Password Filter DLL | medium | windows / process_creation |
| Potential Suspicious Activity Using SeCEdit | medium | windows / process_creation |
None recorded.
| Used by | Procedure example |
|---|---|
| GroupMirrorFace | MirrorFace has used a tool named MRSAStealer as a password filter to collect credentials on password changes. |
| GroupOilRig | OilRig has registered a password filter DLL in order to drop malware. |
| GroupStrider | Strider has registered its persistence module on domain controllers as a Windows LSA (Local System Authority) password filter to acquire credentials any time a domain, local user, or administrator logs in or changes a password. |
Data from MITRE ATT&CK® (Enterprise). ATT&CK® is a registered trademark of The MITRE Corporation.
